Early on Wednesday it was over Tonga's Tongatapu islands, moving south-eastwards away from the country.
Meanwhile Fiji's Red Cross says the country coped well when the storm struck on Monday night.
The aid group says it is been helping people who have not been able to return to their homes.
About 50 houses were destroyed by the storm.
More than 3,800 people were reportedly forced to sleep in evacuation centres because of fears their houses would not withstand the force of the winds.
Fiji Red Cross disaster manager Vuli Gauna says thanks to good preparation by the authorities and the fact that Fiji got plenty of warning, the country handled the situation well.
He said: "Compared to what happened in January with the flooding, we have good capacity with the branches because we have spent significant time preparig for the cyclone season as a result of the flooding.
Fiji's interim attorney-general, Aiyaz Sayed Khaiyum, confirmed Cyclone Mick caused three deaths, but there are fears the toll could rise, as the search continues for two missing fishermen.
- Australian Broadcasting Corporation
- © ABC